Anti-wetting, or superhydrophobic surfaces have been a subject of significant interest in the engineering field for many years, particularly due to the potential to create self-cleaning surfaces. A droplet of water landing on a superhydrophobic surface will roll or slide away, whilst taking with it any surface debris. Such surfaces exist in nature, and there have been many reports where ultra-short pulsed lasers have been used to generate surfaces with similar feature sizes and hydrophobic performance. However it is also possible to produce superhydrophobic surfaces with short (nanosecond) laser pulses. In this paper we report our work in which flat sheets of SS304S15 were textured using a nanosecond pulsed fibre laser operating at 1064 nm. Quantitative analysis of the wettability of the laser structured surfaces was carried out by measuring the static contact angle of a droplet of deionized water with a volume in the microliter range. As with other reports, these surfaces are initially hydrophilic, and after a time delay of some days to weeks transition to hydrophobic, and in some cases to superhydrophobic. In order to realise a practical process, our work has concentrated in speeding up this transition from weeks to days, and to this end we have studied the role of the processing environment during laser texturing.
Recent developments and progress in the delivery of high average power ultrafast laser pulses enable a range of novel minimally invasive surgical procedures. Lung cancer is the leading cause of cancer deaths worldwide and here the resection of lung tumours by means of picosecond laser pulses is presented. This represents a potential alternative to mitigate limitations of existing surgical treatments in terms of precision and collateral thermal damage to the healthy tissue.
Robust process parameters for the laser resection are demonstrated using ovine pulmonary adenocarcinoma (OPA). OPA is a naturally occurring lung cancer of sheep caused by retrovirus infection that has several features in common with some forms of human pulmonary adenocarcinoma, including a similar histological appearance, which makes it ideally suited for this study.
The picosecond laser was operated at a wavelength of 515 nm to resect square cavities from fresh ex-vivo OPA samples using a range of scanning strategies. Process parameters are presented for efficient ablation of the tumour with clear margins and only minimal collateral damage to the surrounding tissue. The resection depth can be controlled precisely by means of the pulse energy. By adjusting the overlap between successive laser pulses, deliberate heat transfer to the tissue and thermal damage can be achieved. This can be beneficial for on demand haemostasis and laser coagulation.
Overall, the application of ultrafast lasers for the resection of lung tumours has potential to enable significantly improved precision and reduced thermal damage to the surrounding tissue compared to conventional techniques.
Local resection of early stage tumors in the large bowel via colonoscopy has been a widely accepted surgical modality for colon neoplasm treatment. The conventional electrocautery techniques used for the resection of neoplasia in the mucosal or submucosal layer of colon tissue has been shown to create obvious thermal necrosis to adjacent healthy tissues and lacks accuracy in resection. Ultrafast picosecond (ps) laser ablation using a wavelength of 1030 or 515 nm is a promising surgical tool to overcome the limitations seen with conventional surgical techniques. The purpose of this initial study is to analyze the depth of ablation or the extent of coagulation deployed by the laser as a function of pulse energy and fluence in an ex-vivo porcine model. Precise control of the depth of tissue removal is of paramount importance for bowel surgery where bowel perforation can lead to morbidity or mortality. Thus we investigate the regimes that are optimal for tissue resection and coagulation through plasma mediated ablation of healthy colon tissue. The ablated tissue samples were analyzed by standard histologic methods and a three dimensional optical profilometer technique. We demonstrate that ultrafast laser resection of colonic tissue can minimize the region of collateral thermal damage (<50 μm) with a controlled ablation depth. This surgical modality allows potentially easier removal of early stage lesions and has the capability to provide more control to the surgeon in comparison with a mechanical or electrocautery device.
Endoscopic resection of early colorectal neoplasms typically employs electrocautery tools, which lack precision and run the risk of full thickness thermal injury to the bowel wall with subsequent perforation. We present a means of endoluminal colonic ablation using picosecond laser pulses as a potential alternative to mitigate these limitations. High intensity ultrashort laser pulses enable nonlinear absorption processes, plasma generation, and as a consequence a predominantly non-thermal ablation regimen.
Robust process parameters for the laser resection are demonstrated using fresh ex vivo pig intestine samples. Square cavities with comparable thickness to early colorectal neoplasms are removed for a wavelength of 1030 nm and 515 nm using a picosecond laser system. The corresponding histology sections exhibit in both cases only minimal collateral damage to the surrounding tissue. The ablation depth can be controlled precisely by means of the pulse energy. Overall, the application of ultrafast lasers for the resection of intestine enables significantly improved precision and reduced thermal damage to the surrounding tissue compared to conventional electrocautery.
Lasers have been previously been used for dental applications, however there remain issues with thermally-induced
cracking. In this paper we investigate the impact of pulse length on CO2 laser ablation of human dental enamel.
Experiments were carried in vitro on molar teeth without any modification to the enamel surface, such as grinding or
polishing. In addition to varying the pulse length, we also varied pulse energy and focal position, to determine the most
efficient ablation of dental hard tissue and more importantly to minimize or eradicate cracking. The maximum
temperature rise during the multi pulse ablation process was monitored using a set of thermocouples embedded into the
The application of a laser device in dental surgery allows removal of tissue with higher precision, which results in
minimal loss of healthy dental tissue. In this study we use an RF discharge excited CO2 laser operating at 10.6μm. The
wavelength of 10.6 μm overlaps with a phosphate band (PO3-4) absorption in dental hard tissue hence the CO2 laser
radiation has been selected as a potential source for modification of the tissue. This research describes an in-depth
analysis of single pulse laser ablation. To determine the parameters that are best suited for the ablation of hard dental
tissue without thermal cracking, a range of pulse lengths (10-200 μs), and fluences (0-100 J/cm2) are tested. In addition,
different laser focusing approaches are investigated to select the most beneficial way of delivering laser radiation to the
surface (divergent/convergent beam).
To ensure that these processes do not increase the temperature above the critical threshold and cause the necrosis of the
tissue a set of thermocouples was placed into the pulpal chambers. Intermittent laser radiation was investigated with and
without application of a water spray to cool down the ablation site and the adjacent area. Results show that the
temperature can be kept below the critical threshold either by using water spray or by decreasing the repetition rate. We
demonstrate that CO2 laser pulses with pulse lengths in the regime of 10 μs can provide precise enamel tissue removal
without introducing any unwanted thermal damage.
Endoluminal surgery for the treatment of early stage colorectal cancer is typically based on electrocautery tools which imply restrictions on precision and the risk of harm through collateral thermal damage to the healthy tissue. As a potential alternative to mitigate these drawbacks we present laser machining of pig intestine by means of picosecond laser pulses. The high intensities of an ultrafast laser enable nonlinear absorption processes and a predominantly nonthermal ablation regime.
Laser ablation results of square cavities with comparable thickness to early stage colorectal cancers are presented for a wavelength of 1030 nm using an industrial picosecond laser. The corresponding histology sections exhibit only minimal collateral damage to the surrounding tissue. The depth of the ablation can be controlled precisely by means of the pulse energy. Overall, the application of ultrafast lasers to ablate pig intestine enables significantly improved precision and reduced thermal damage to the surrounding tissue compared to conventional techniques.
The use of ultrafast lasers (pulsed lasers with pulse lengths of a few picoseconds or less) offers the possibility for minimally invasive removal of soft ophthalmic tissue. The potential for using pico- and femtosecond pulses for modification of scleral tissue has been reported elsewhere [1-6] and has resulted in the introduction of new, minimally invasive, procedures into clinical practice [3, 5-10]. Our research is focused on finding optimal parameters for picosecond laser machining of scleral tissue without introducing any unwanted collateral damage to the tissue. Experiments were carried out on hydrated porcine sclera in vitro, which has similar collagen organization, histology and water content (~70%) to human tissue. In this paper we present a 2D finite element ablation model which employs a one-step heating process. It is assumed that the incident laser radiation that is not reflected is absorbed in the tissue according to the Beer-Lambert law and transformed into heat energy. The experimental setup uses an industrial picosecond laser (TRUMPF TruMicro 5x50) with 5.9 ps pulses at 1030 nm, with pulse energies up to 125 μJ and a focused spot diameter of 35 μm. The use of a scan head allows flexibility in designing various scanning patterns. We show that picosecond pulses are capable of modifying scleral tissue without introducing collateral damage. This offers a possible route for minimally invasive sclerostomy. Many scanning patterns including single line ablation, square and circular cavity removal were tested.
Ultrafast lasers offer a possibility of removing soft ophthalmic tissue without introducing collateral damage at the ablation site or in the surrounding tissue. The potential for using ultrashort pico- and femtosecond pulse lasers for modification of ophthalmic tissue has been reported elsewhere and has resulted in the introduction of new, minimally invasive procedures into clinical practice. Our research aims to define the most efficient parameters to allow for the modification of scleral tissue without introducing collateral damage. Our experiments were carried out on hydrated porcine sclera invitro. Porcine sclera, which has similar collagen organization, histology and water content (~70%) to human tissue was used. Supporting this work we present a 2D finite element blow-off model which employs a one-step heating process. It is assumed that the incident laser radiation that is not reflected is absorbed in the tissue according to the Beer-Lambert law and transformed into heat energy. The experimental setup uses an industrial picosecond laser (TRUMPF TruMicro 5x50) with 5.9 ps pulses at 1030 nm, with pulse energies up to 125 μJ and a focused spot diameter of 35 μm. Use of a beam steering scan head allows flexibility in designing complicated scanning patterns. In this study we have demonstrated that picosecond pulses are capable of removing scleral tissue without introducing any major thermal damage which offers a possible route for minimally invasive sclerostomy. In assessing this we have tested several different scanning patterns including single line ablation, square and circular cavity removal.
Lasers have been shown to be successful in certain medical procedures and they have been identified as potentially making a major contribution to the development of minimally invasive procedures. However, the uptake is not as widespread and there is scope for many other applications where laser devices may offer a significant advantage in comparison to the traditional surgical tools. The purpose of this research is to assess the potential of using a picosecond laser for minimally invasive laser sclerostomy. Experiments were carried out on porcine scleral samples due to the comparable properties to human tissue. Samples were prepared with a 5mm diameter trephine and were stored in lactated Ringer’s solution. After laser machining, the samples were fixed in 3% glutaraldehyde, then dried and investigated under SEM. The laser used in the experiments is an industrial picosecond TRUMPF TruMicro laser operating at a wavelength of 1030nm, pulse length of 6ps, repetition rate of 1 kHz and a focused spot diameter of 30μm. The laser beam was scanned across the samples with the use of a galvanometer scan head and various ablation patterns were investigated. Processing parameters (pulse energy, spot and line separation) which allow for the most efficient laser ablation of scleral tissue without introducing any collateral damage were investigated. The potential to create various shapes, such as linear incisions, square cavities and circular cavities was demonstrated.
The purpose of this paper is to present a design procedure and experiment results for a continuous-action fiberoptic
laser based on PM-Er-PCF (polarization-maintaining erbium-doped photonic crystal fiber). To the best of our
knowledge, it's the first erbium-doped photonic fiber that maintains polarization. Stable single-wavelength actions were
observed in a laser ring configuration. A PM-Er-PCF optimization and an analysis of photonic crystal structure's impact
on laser parameters are demonstrated in the theoretical part of this article. The presented fiber laser can be used as a
signal source in WDM systems.